Phytobiotics are promising dietary tools to improve metabolic stability and physiological resilience against chemical stressors in aquaculture. This study evaluated nrf2-linked antioxidant and metabolic modulation by dietary Origanum vulgare essential oil (OEO) in Nile tilapia (Oreochromis niloticus) under malathion-induced organophosphate stress. Fish, with an initial weight of 5.76 ± 0.56 g, were distributed in three tanks per treatment, with 15 fish per tank, and fed diets containing 0 (control), 0.75, 1.50, 2.25 and 3.00 g kg−1 OEO for eight weeks, followed by exposure to malathion (7.04 mg L−1) for 96 h. OEO enhanced (p < 0.05) growth performance, feed utilisation, and survival after exposure, with the greatest productive and survival outcomes at 3.00 g kg−1. Fish that received the supplement also had lower (p < 0.05) lipid peroxidation, better antioxidant enzyme activity and a more favourable modulation of nrf2, gpx and keap1 expression, together with biochemical and histological patterns that were consistent with a better condition of the liver and kidney. The heatmap and PCA supported a treatment-related separation, with 2.25 and 3.00 g kg−1 OEO showing the most favourable integrated physiological profiles. Dietary OEO was associated with antioxidant, metabolic and tissue-level resilience linked to modulation of nrf2-related transcriptional responses.
Méndez‐Martínez et al. (Fri,) studied this question.